1. Field of the Invention
The present invention relates to a manufacturing method for a buried insulating layer-type semiconductor silicon carbide substrate and to a manufacturing apparatus thereof.
2. Prior Art
Single crystal silicon carbide (SiC) has been focused on as a material for semiconductor devices of the next generation because of its characteristics wherein single crystal silicon carbide is excellent in thermal and chemical stability, has a high mechanical strength and is stable when exposed to radiation. In addition, an SOI substrate having a buried insulating layer is excellent in achieving an increase in the speed of a circuit and a reduction in power consumption and, therefore, is expected to be used as an LSI substrate of the next generation. Accordingly, a buried insulating layer-type semiconductor silicon carbide substrate having these two characteristics is, therefore, expected to be used as a material for semiconductor devices.
At present, however, a manufacturing method for a buried insulating layer-type semiconductor silicon carbide substrate having the characteristics of single crystal silicon carbide and an SOI substrate has not yet been established.
As for a method for forming a single crystal silicon carbide thin film on a silicon substrate, a plasma-type vapor phase reaction, or the like, for example, maybe carried out on a silicon substrate and it is possible to apply such a technique to an SOI substrate so that a single crystal silicon carbide thin film is formed on the SOI substrate. In addition, at present, the film thickness of the surface silicon layer in an SOI substrate exceeds 50 nm.
There is a problem with a semiconductor substrate that has been manufactured according to a method for forming a single crystal silicon carbide thin film on an SOI substrate wherein a silicon layer is intervened between the single crystal silicon carbide thin film and the buried insulator. A problem arises wherein such a silicon layer intervened between a single crystal silicon carbide thin film and a buried insulator diffuses into the single crystal silicon carbide thin film on the surface of the substrate during a heat treatment in a later process leading to the deterioration of the physical characteristics thereof. In addition, the desired structure wherein silicon carbide is formed on the buried insulator is not gained.
In addition, a film formation process must be carried out in a high vacuum according to a method for forming a single crystal silicon carbide thin film on an SOI substrate by means of a plasma-type vapor phase reaction, or the like, and, therefore, a manufacturing apparatus having a complex structure is required. A problem wherein the cost for the formation of a single crystal silicon carbide thin film is increased is of course involved with such a manufacturing apparatus due to its complex structure.
In addition, in the case of an SOI substrate having a surface silicon layer of which the film thickness exceeds 10 nm, the metamorphoseed single crystal silicon carbide thin film locally causes nucleus growth leading to the formation of grains and, thereby, the surface of the substrate becomes coarse, bringing about an unfavorable condition.